EFFICIENT, CONVENIENT, AND affordable transportation systems are viewed as an essential component for social and economic development. The United Nations (UN) has called for concerted action on transport issues in its 1992 Agenda 21 Program and the 2002 Johannesburg Plan of Implementation. However, because transport is a major source of atmospheric emissions, it must be carefully designed and managed so as to be sustainable—environmentally, socially, and economically—in the long term. Transport involves the movement of people and goods, and falls into three sectors: Air, sea, and land.
Air transport has only existed for approximately 100 years; however, the consistent growth of this sector has raised concerns about its environmental impacts. Airplanes release pollutants associated with the combustion of fossil fuels, such as carbon dioxide, carbon monoxide, nitrogen oxides, sulfur oxides, volatile organic compounds, particulates, and other trace compounds. These pollutants are released into the upper troposphere and lower stratosphere, where they have an impact on atmospheric composition. A report issued in 1999 by the International Panel on Climate Change summarized the ecological impacts of aviation: Aircraft emit gases and particles that alter the atmospheric concentration of greenhouse gases, trigger the formation of condensation trails, and may increase cirrus cloudiness, all of which contribute to climate change; and aircraft are estimated to contribute about 3.5 percent of the total radiative forcing (a measure of change in climate) by all human activities and that this percentage, which excludes the effects of possible changes in cirrus clouds, is projected to grow. Emissions from aircraft are not included in targets set by the Kyoto Protocol of the UN Framework Convention on Climate Change (UNFCCC), though the Protocol does state that Annex I Parties do have the responsibility to limit or reduce greenhouse gas emissions from aviation fuels.
Sea transport is used primarily for long-distance shipping of goods. Two prime environmental concerns are the disposal of pollutants into the sea (marine or ocean dumping), and the introduction of alien invasive species through ocean transportation. Marine dumping occurs either accidentally, as is the case with oil spills, or intentionally through dredging spoil, nuclear waste disposal, sewage outfalls, and cruise ship waste. Various international agreements have been agreed to address intentional disposal of wastes at sea, such as the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (that is, the London Convention of 1972).
Introduction of alien invasive species is the second biggest threat to biodiversity after habitat loss. In terms of marine invasive species, a common method of transmission has been through ballast water, which “is now regarded as the most important vector for trans-oceanic and inter-oceanic movements of shallow-water coastal organisms,” according to the World Conservation Union (IUCN). However, species can also attach themselves to the hulls of ships and be transported in that way. Examples of the introduction of alien invasive species by ballast water or hull fouling include the spread of zebra mussels into the North American Great Lakes water system.
Land transport mainly refers to road and rail modes; road transport can be further divided into motorized and nonmotorized traffic. Nonmotorized transport is comprised primarily of walking and cycling, though other forms do occur, such as wheelbarrows, handcarts, pack donkeys, sledges, and animal-drawn carts. Nonmotorized transport has a number of environmental advantages, the most obvious of which is the minimal or nil production of emissions. Nonmotorized transport is also an integral element of transport for people in developing countries, who may not be able to afford private motorized vehicles or even public transport. Nonmotorized transport has been considered one of the most viable methods of addressing social and economic development issues in developing countries. Cycling is a common form of nonmotorized transport, and infrastructure for cyclists can also be integrated into public transport networks in order to improve accessibility and convenience.
Rail transport is generally more energy efficient than road transport, but despite this, in many regions of the world, rail freight and passenger numbers are decreasing. Light rail systems are gaining popularity as an urban transportation option in many countries, and can be found in: Cairo, Egypt; Kuala Lumpur, Malaysia; Christchurch, New Zealand; Manila, the Philippines; Geneva, Switzerland; and Bangkok, Thailand. These rail systems can be in the form of trains, tramways, or trolleys/streetcars. Other rail-based urban transport systems include subways/metros (underground) and monorail (elevated) systems.
Reduced environmental impacts from motorized road transport are possible through technological improvements in two main areas: Vehicle technology and fuel quality. Fuel quality has improved greatly over the past 30 years, and is continuing to improve. Unleaded petrol, first introduced in the 1970s, is now available in most countries around the world, and many countries are reducing the concentrations of sulfur and other substances in petrol and diesel fuels. Alternative fuels have also emerged, such as biodiesel and compressed natural gas.
However, many newer and cleaner fuels require more advanced vehicle technologies. Therefore, vehicle engines have consistently become more fuel-efficient, and many countries have been implementing stricter regulations to encourage further advances in vehicle efficiency. In addition, new vehicle components have been developed that reduce the volume of pollutants that are released from vehicles, such as particulate filters and catalytic converters. Most recently, through the development of new ways of powering vehicles, low or no emission vehicles are now available, such as hybrid-electric vehicles. As research and development in this area increases, the availability, affordability, and efficiency of these vehicles will grow. Innovations in fuel quality and vehicle technology can result in substantial improvements to air quality and human health.
Transportation issues vary between rural and urban areas. Transport in rural areas is critical in that these areas tend to be inhabited by poorer segments of the population. In South Africa, for example, half of the population is rural, but 72 percent of those living in the rural areas are poor, according to the South African National Department of Transport. Because rural transport links tend to service the poor, it is essential that they are cost-effective. Provision of affordable and well-maintained transport links for people and for goods is essential, especially in terms of strategies to increase economic development and reduce poverty in these areas.
In urban areas, where there is high population density and therefore a greater need for the movement of goods and people, congestion caused by traffic is a significant problem. The built environment of urban areas is often not designed for high volumes of vehicular traffic, and prevents the dispersion of emissions, and pollutants remain in the urban street canyons, resulting in poor air quality. Moreover, increasing urbanization and personal vehicle use can result in urban sprawl. Expansion of low-density metropolitan areas outside of urban centers can reduce the cost-effectiveness and efficiency of alternative transport options such as mass transit, and exacerbate the need for personal vehicle use. Therefore, transport planning is an essential part of any urban, regional, or national infrastructure strategy. Comprehensive and forward-looking plans are necessary for a rational transport infrastructure that supports current and future needs of society and is environmentally sustainable.
Public transport is viewed as a mobility option that has environmental and social benefits. From an environmental perspective, the higher density of people being transported in less vehicles results in lower energy inputs, lower emissions, and less space required for roads and parking areas. Social benefits are also gained from efficient public transport systems: enriched social contacts, increased time for activities such as reading, and lower risk of being involved in traffic accidents. A number of cities around the world, including those in developing countries, have undertaken a range of highly innovative land transport policy and projects that promote social and economic development and that address the environmental impacts from transport.
Bogotá, Colombia has redesigned some of its transportation infrastructure to support nonmotorized traffic. For example, it has built about 120 kilometers of bicycle routes throughout the city, and has instituted a policy by which all cars are banned from over 100 kilometers of the city’s main roads on Sundays and holidays, providing a safe space for cyclists. With these innovations, the number of cyclists in Bogotá has increased dramatically: the number increased from 0.1 percent of the population in 1997, to five percent of the population in 2001.
In 2003, London instituted congestion charges for driving in central London during certain peak hours. In addition, the transport strategy also has provisions for extra buses and the introduction of new routes. By early 2004, congestion levels during weekdays had fallen by one-third of the previous amount. In 1998 the Indian Supreme Court handed down a judgment with a list of measures to be taken to address air pollution. In order to comply with that judgment, all buses had to be converted to compressed natural gas (CNG) by the end of March 2001. Delhi currently has over 80,000 CNG vehicles on the road, including 9,000 buses. Pressured with quickly growing urban populations, Curitiba, Brazil started implementing express bus lanes in 1974. As of 2001, 75 percent of Curitiba’s commuters used the bus system (over 1.9 million passenger trips each day), and the city’s transport network included 58 kilometers of express bus lanes, 270 kilometersof feeder routes, and 185 kilometers. of inter-district routes.
Automobiles; Bicycles; Cities; Fate and Transport of Contaminants; Flight; Highways; Hybrid Vehicles; Marine Pollution; Oil Spills; Pollution, Air.
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